Evaluation of Nine Native Plant Species Planted in Four Growth Media Depths for Extensive Green Roof

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Evaluation of Nine Native Plant Species Planted
in Four Growth Media Depths for Extensive Green
Roofs

• 1L. Richter, 1W. Retzlaff, 1S. Morgan, 2K.
  Luckett, 3V. Jost.
• 1Southern Illinois University Edwardsville, IL,
• 2Green Roof Blocks, St. Louis, MO,
• 3Jost Greenhouses, Des Peres, MO.

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Extensive Green Roof Conditions

• High solar radiation
• Extra high evaporation
• Long periods where arid soils may occur (Kohler,
  2003)
• Selecting plants with xerophytic characteristics
  may be important for green roof applications
  (Martin Hinckley, 2007)

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Plant Selection

• Groups other than Sedum possess adaptations to
  similarly extreme temperature and moisture
  conditions
• Drought tolerance, high seed production, short
  lived-cycle (Kohler, 2003)
• Possible species occurs in habitats such dry
  grassland or steppe (Dunnett and Nolan, 2004) and
  rock outcrops, cliffs and alpine areas (Lundholm
  et al., 2009)

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Previous Studies MSU

• Evaluated 18 Michigan natives and 9 Sedum spp.
• 4 of 18 natives were used successfully
• All Sedum spp. were suitable for an extensive
  green roof without irrigation

(Monterusso et al., 2005)
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Previous Studies Nova Scotia, Canada

• Evaluated 14 species and 3 moisture treatments
  (4, 11, and 24 days between saturation)
• Dry treatment only 3 species lived (Sedum
  rubrotinctum, Sedum spurium, and Rhodiola rosea)
• Wet treatments all 14 species survived

(Wolf and Lundholm, 2008)
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Previous Studies UK

• Evaluated 9 herbaceous perennials and 2 substrate
  depths
• There is a potential to use other species on
  extensive green roofs, and substrate depth may be
  less important than water availability

(Dunnett and Nolan, 2004)
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Increasing Potential Plant Palette

• Larger plant selection could encourage
  biodiversity, replace habitat lost by
  development, and add green space in urban
  environments (Bousselot et al., 2009)
• Extensive green roofs can be designed for
  different plant taxa (Brenneisen, 2006 Kohler,
  2006) and provide valuable wildlife habitat
  (Grant, 2006 Baumann, 2006 Kadas, 2006)

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Project Goal

• Monitor plant performance of 9 perennial species
  in 4 green roof substrate depths, and evaluate
  suitability for a midwest extensive green roof.

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Methods

• June 11, 2009 at SIUE Environmental Sciences
  Field Site
• Green PaksTM modular system
• Nine native plant species
• Four growth media depths (7, 16, 24, 33 cm)

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Native green roof study experimental layout at
SIUE field site. Within a replicate there were
two Green PaksTM at each substrate depth (7, 16,
24, and 33 cm), and there were three replicates.
To attain the different substrate depths we
stacked Green PaksTM 1 (7 cm), 2 (16 cm), 3 (24
cm), and 4 (33 cm) deep.
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Native green roof study experimental layout at
SIUE field site for pack depth and plant
locations. Species codes are, Allium
schoenoprasum (ALSC ), Antennaria dioica (rubra)
(ANDI), Bouteloua gracilis (BOGR), Callirhoe
involucrata (CAIN), Ericameria nauseosus (ERNA),
Eryngium yuccifolium (ERYU), Oryzopsis hymenoides
(ORHY), Ruellia humilus (RUHU), and Talinum
calycinum (TACA).  
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Antennaria dioica (rubra)
Allium schoenoprasum
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Callirhoe involucrata
Bouteloua gracilis
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Eryngium yuccifolium
Ericameria nauseosus
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Oryzopsis hymenoides
Ruellia humilis
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Talinum calycinum
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Measurements

• Percent roof coverage using modified dot grid
• Plant growth index (H X W1 X W2)/3
• (Monterusso et al., 2005)

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Percent roof coverage in relation to growth
medium depth on 07/08/09. Letters that are the
same are not significantly different at an a
level 0.05. Bars represent 1 standard error.
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Percent roof coverage in relation to growth
medium depth on 07/22/09. Letters that are the
same are not significantly different at an a
level 0.05. Bars represent 1 standard error.
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Plant species growth index on 07/08/09. Growth
index represent average of height, and two width
measurements. Species codes are, Allium
schoenoprasum (ALSC ), Antennaria dioica (rubra)
(ANDI), Bouteloua gracilis (BOGR), Callirhoe
involucrata (CAIN), Ericameria nauseosus (ERNA),
Eryngium yuccifolium (ERYU), Oryzopsis hymenoides
(ORHY), Ruellia humilus (RUHU), and Talinum
calycinum (TACA). Letters that are the same are
not significantly different at an a level 0.05.
Bars represent 1 standard error.
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Plant species growth index on 07/22/09. Growth
index represent average of height, and two width
measurements. Species codes are, Allium
schoenoprasum (ALSC ), Antennaria dioica (rubra)
(ANDI), Bouteloua gracilis (BOGR), Callirhoe
involucrata (CAIN), Ericameria nauseosus (ERNA),
Eryngium yuccifolium (ERYU), Oryzopsis hymenoides
(ORHY), Ruellia humilus (RUHU), and Talinum
calycinum (TACA). Letters that are the same are
not significantly different at an a level 0.05.
Bars represent 1 standard error.
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Conclusions

• After 6 weeks of growth there was no difference
  in overall percent roof coverage by depth, but
  individual species did show differences in growth
  indices.
• Percent roof coverage and growth index
  measurements will continue for several years to
  evaluate which growth medium depths, if any, are
  suitable for each of the species.

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References

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• Bousselot, J.M., Klett, J.E., Kosk, R.D. 2009.
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• Brenneisen, S. 2006. Space for Urban Wildlife
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• Dunnett, N., Nolan, A. 2004. The Effect of
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• Monterusso, M.A., Rowe, D.B., Rugh, C.L. 2005.
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Acknowledgements

• We thank the National Great Rivers Research and
  Education Center for funding this internship.